Question: $ { {-3} \times \left[\begin{array}{rrr}{1} & {-1} & {3} \\ {3} & {1} & {1}\end{array}\right] = {?} } $
Solution: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rrr}{-3}\times{1} & {-3}\times{-1} & {-3}\times{3} \\ {-3}\times{3} & {-3}\times{1} & {-3}\times{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-3} & {3} & {-9} \\ {-9} & {-3} & {-3}\end{array}\right]}$